When communicating with other devices, mobile devices such as cell phones transmit radiation in the form of communication signals. The transmitted radiation may be received and be reflected, passed, and/or absorbed by nearby objects. Living objects, such as humans, may absorb the radiation emitted by a mobile device and be harmed thereby. The closer the living object is to the transmitting antenna of the device, the more radiant energy that is absorbed. For example, the head, an ear, or a hand of a human using a cell phone to make a phone call may absorb a substantial amount of the transmitted radiation.
Accordingly, specific absorption rate (SAR) testing is being required for mobile devices to protect humans from the emitted radiation. SAR is a measure of the rate at which energy is absorbed by the human body when exposed to a radio frequency (RF) electromagnetic field. Various governments have defined maximum SAR levels for RF energy emitted by mobile devices.
Current techniques for object detection are implemented through circuitry. For example, a resonance circuit may be connected to a sense antenna. When an object approaches the sense antenna, the resonance frequency shifts. The resonance frequency shift can be measured, and a particular amount of shift may indicate that a nearby object is detected. Another technique uses IR (infrared) LEDs (light emitting diodes) with IR sensors to emit light and measure the light reflected back.